the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Sep 2023
Measurement report: Violent biomass burning and volcanic eruptions: a new period of elevated stratospheric aerosol over Central Europe (2017 to 2023) in a long series of observations
Abstract. The highlight of the meanwhile 50 years of lidar-based aerosol profiling at Garmisch-Partenkirchen has been the measurements of stratospheric aerosol since 1976. After a technical breakdown in 2016, they have been continued with a new, much more powerful system in a vertical range up to almost 50 km a.s.l. that allowed to observe very weak volcanic aerosol up to almost 40 km. The observations since 2017 are characterized by a number of spectacular events, such as the Raikoke volcanic plume equalling in integrated backscatter coefficient that of Mt. St. Helens in 1981 and severe smoke from several big fires in North America and Siberia with backscatter coefficients up to the maximum values after the Pinatubo eruption. The smoke from the violent 2017 fires in British Columbia gradually reached more than 20 km a.s.l., unprecedented in our observations. The sudden increase in frequency of such strong events is difficult to understand. Finally, the plume of the spectacular underwater eruption on the Tonga islands in the southern Pacific in January 2022 was detected between 20 and 25 km.
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CC1: 'Comment on egusphere-2023-1781', Albert Ansmann, 18 Oct 2023
Dear Thomas and colleagues!
I read the manuscript with great interest. It is amazing to see this almost 50 year long time series of stratospheric aerosol observations, from 1976 to 2023.
The title of the manuscript points to the recent years (2017-2023) with a strong contribution of wildfire smoke to the aerosol in the stratosphere.
Because we from TROPOS worked a lot on this topic (and published several papers on wildfire smoke) I was forced to write a short comment.
Line 36: Yes, Mike Fromm pushed the smoke research forward (six references), but one could add even papers of Ohneiser et al. (ACP, 2022) on long term observations of Australian smoke (2020-2021) and Baars et al. (ACP) on Europe-wide Canadian smoke observations in 2017-2018.
line 42: The decay time should be well defined in the paper. The e-folding decay time was 13-15 months in the case of Pinatubo over Northern Germany (Ansmann, JAS, 1997) and 1.14 and 1.37 years over Japan and New Zealand (Nagai et al., SOLA, 2010, https://doi.org/10.2151/sola.2010-018).
line 60: Baars et al. (2019)
line 77: Are you sure that the Colorado fires were responsible for the smoke pollution in 2020? There were also long-lasting record breaking Californian fires during the 2020 summer half year, as described in Hu et al. (2022) and Mamouri et al. (ACPD, 2023).
line 261: …to more than 20 km (e.g., Baars et al. 2019, Torres et al., JGR, 2020 10.1029/2020JD032579).
line 285: Meanwhile it seems to be well established that pyroCb lofting followed by significant self lofting (as long as the smoke optical depth is high, during the first days after injection) enables the smoke to reach heights of more than 20 km or even more than 30 km (Torres et al, 2020, Khaykin et al., 2018, 2020, Ohneiser et al., 2023). There are many more papers on this topic in the recent literature.
line 297: For the same reason (impact of these lofting processes), the main message regarding the use and applicability of HYSPLIT trajectories should be that such a trajectory analysis can only describe the smoke transport when the lofting processes are (widely) over, when the smoke reached already heights in the lower stratosphere. The impact of pyroCbs and self lofting are not considered in these trajectory simulations.
line304: hot pyroCb is misleading….. after dissolution of the ‘cold’ pyroCb-related cirrus umbrella, smoke absorption and self lofting takes over.
line 332: Also the lidar at Hohenpeissenberg detected the aerosol in the free troposphere on 2 October 2017.
lines 343-345: In this context one should provide the reference to the paper in which the Leipzig observation are presented and discussed: Ansmann, Frontiers in Environ. Sci., 2021, doi: 10.3389/fenvs.2021.769852.
line 352: You assume that the smoke originated from strong Colorado fires? The articles of Hu et al., ACP, 2022, doi.org/10.5194/acp-22-5399-2022, Michailidis et al., ACP, 2023, doi.org/10.5194/acp-23-1919-2023, and Mamouri et al, ACPD, 2023 report smoke from record-breaking Californian fires. Maybe check again to be sure that Colorado fires were dominating.
line 403: To repeat, pyroCb contributes to the lofting of smoke, but also subsequently occurring self lofting of smoke.
line 414: You mean Boone et al. (2022)!
line 422: Do you think you observed volcanic ash or volcanic sulfate? Please discuss a bit.
line 550: Stenchikov et al. (2022) describes a similar scenario for Pinatubo aerosol as I tried to describe it for the smoke above. Pinatubo ash (plus SO2) was lofted (injected) up to about 17 km and then self lofting (as a result of absorption of solar radiation by ash particles) lofted the entire volcanic pollution higher up to 25-30km height (within a few days…). Then self lofting stopped because the high optical depth of ash disappeared by dilution and by sedimentation of ash particles. Then the sulfate layer formed in these lofted plumes with maximum heights around 30 km.
Figure 2: I do not understand! Please state clearly what you did! I speculate you applied the ozone correction to the lidar signals first and afterwards you applied the Klett method to the ozone-corrected signal profiles?
Figure 7: Californian or Colorado smoke?
Figure 10: Such a profile structure with aerosol within the upper troposphere as well as in the lower stratosphere on 22 August 2019 (red profile) was also found over Leipzig on 14 August 2019 (Ansmann et al., Frontieres, 2021) and assigned as smoke layer because of the high 532 nm lidar ratios (unusually high compared to volcanic sulfate lidar ratios published by Horst Jaeger). The fact that the aerosol layer was not clearly above the tropopause seems to be a hint that this is some kind of an undefined aerosol layer, partly containing smoke in the lower part and volcanic sulfate in the upper part.
All in all a nice…., or better an excellent work!
Citation: https://doi.org/10.5194/egusphere-2023-1781-CC1 -
RC1: 'Comment on egusphere-2023-1781', Juan Carlos Antuna-Marrero, 20 Oct 2023
The manuscript reports the characterization of the stratospheric aerosols layer enhancements over Central Europe produced by explosive volcanic eruptions and severe smoke from big fires. To that end, lidar observations between 2017 and 2023 at Garmisch-Partenkirchen, one of the longest stratospheric aerosols lidar records is used. It has been extensively used for research up to the present as the references show.
The manuscript’s scientific significance and scientific quality are excellent. The presentation is also excellent.
The description of the main features of the lidar instrumentation evolution and the most relevant aspects of the retrieved signal processing are included appropriately. Also, the discussion in the Annex of the contributions to the aerosol backscatter uncertainties is very important. It addresses relevant scientific questions for ACP Journal, in particular the characterization of the vertical and temporal evolution of the stratospheric aerosol optical properties originated from severe smoke from big fires and explosive volcanic eruption. All those facts warrantees the traceability of the results. The time frame are the last 6 years in which the frequency of those severe smoke from big fires has increased without a plausible explanation so far.
The scientific results and conclusions are presented in a clear, concise, and well structures way with an appropriate number of figures and tables. It gives appropriate credit to similar research and clearly indicates its own contribution. The manuscript title is appropriated, reflecting its content. Similarly, the abstract provides a concise and complete summary.
The references area appropriated in quality and number as well as the supplementary material.
I have some comments and suggestions listed below.
Comments:
In the section “Spectacular pyro-cumulonimbus in British Columbia on 30 June 2021”, the Figure 8 shows the aerosol backscatter uncertainty profile allowing to appreciate its reasonable magnitude respect to the aerosol backscatter. However, that is not possible for the two peaks going beyond the border of the figure. I suggest the authors include a brief description of the relative magnitudes of the uncertainties at the peaks in comparison with the relative magnitudes of the uncertainties from the rest of the profile.
Line 26: In the sentence: Ground-based lidar with its good vertical resolution became an important tool “almost” right from the beginning…. I suggest eliminating the word “almost” and add 2 more references: Fiocco, G., and G. Grams, 1964 and Elterman et al., 1973.
The first series of stratospheric aerosol profiles from lidar (Fiocco, G., and G. Grams, 1964, https://doi.org/10.1175/1520-0469(1964)021<0323:OOTALA>2.0.CO;2 ) and from searchlight (Elterman, et al., 1964, https://doi.org/10.1175/1520-0469(1964)021<0457:AAOWSP>2.0.CO;2) were extensively used for research on stratospheric aerosol from the middle of the sixties (after the Mt Agung eruption) until around the end of the seventies. They contributed to characterize the volcanic stratospheric aerosols vertical profiles evolution and the further advance of the scientific knowledge in the sixties and early seventies of the XX century. That is evidenced by the multiple articles referencing those results, including the references to Fiocco and Elterman provided in the two papers already cited in that sentence: McCormick et al., 1978; Simonich and Clemesha, 1997.
Elterman himself carried out research using Fiocco´s and his own datasets, (ex. Elterman et al., 1973 https://doi.org/10.1364/AO.12.000330; Elterman,1976 https://opg.optica.org/ao/abstract.cfm?URI=ao-15-5-1113).
Line 342: For clarity I suggest to change the sentence: ” The high lidar ratio suggested that observed at stratospheric aerosol at high latitudes were caused by import of fire smoke from Siberia.…”
By “The observed stratospheric aerosol high lidar ratio suggest its origin was the fire smoke from Siberia”
Line 487: Is this sentence referring to figure 18.? There is not an October 19 profile in the figure, unless the one from that month was labeled as October 10, before the date cited in the sentence.
Line 1020: The link http://www.trickl.de/Rayleigh.pdf does not work.
Figure 3: 4th line in the caption. The acronym “PSC” is not defined in the text, been used commonly for Polar Stratospheric Clouds. The Quebec (1991) and Chilshom (2001) fires mentioned do not appear to be related to PSC events. Please correct or clarify it.
Figures 7: Add the wavelength the aerosol backscatter coefficient was measured.
Figure 12: Briefly describe in the text the criteria to determine the upper and secondary boundaries of the top aerosol layer or provide a reference where it is described. Clarify the term main layer. Include in the caption the wavelength of the SCR. I suggest using the right axes scale for labeling the SCR magnitudes.
Citation: https://doi.org/10.5194/egusphere-2023-1781-RC1 -
RC2: 'Comment on egusphere-2023-1781', Sergey Khaykin, 30 Oct 2023
Review of Trickl et al., “Measurement report: Violent biomass burning and volcanic eruptions: a new period of elevated stratospheric aerosol over Central Europe (2017 to 2023) in a long series of observations”.
The manuscript by Dr. Thomas Trickl and coauthors presents the updated time series of stratospheric integrated backscatter from the 50-yr long lidar profiling record at Garmisch-Partenkirchen and focuses on the lidar observations of stratospheric aerosol layers produced by intense wildfires and volcanic eruptions since 2017.
The authors should be congratulated for an impressive effort to produce such a long-term and high-quality observation record of stratospheric aerosol loading as well as for their rigorous approach to data quality and error budget assessement.
The manuscript is well structured, the experimental setup and the quality aspects are described in a comprehensive way, whereas an appropriate credit is given to the related literature. Overall, the study represents a valuable contribution to the stratospheric aerosol problematics from the observational perspective.
In my opinion, the study could potentially be a good match for the “Research article” category had it included a more profound analysis of the locally observed features (beyond attribution to a specific event using simple trajectory modeling), or had it provided new information on the aerosol optical properties from various sources or otherwise re-evaluated different transport pathways and their timescales. While there are several novel aspects invoked (e.g. BDC-driven transport of aerosols, prolonged stratospheric aerosol decay etc.), the related interpretation largely rests upon general considerations without appropriate support from other data sources, in particular the global observations.
The high-quality local observations presented in the paper will surely motivate further research on the topic using global observations and modeling experiments. Therefore, in no way the “Measurement report” category could reduce the scientific impact of this paper. I recommend it for publication in ACP after a few minor revisions as suggested below.
Specific remarks
l.336-337. It is indeed very interesting (and also puzzling) why the backscatter enhancements are restricted to the lower part of the ozone enhancements. Could it be linked to aerosol sedimentation within the intruded airmass? I would be extremely curious to see the time curtains of backscatter (or just the range corrected signal) together with ozone curtain if this is not too much work.
l.379. Is the upper boundary of enhanced aerosol layer at 19.5 km attributed to wildfire smoke? To my knowledge, neither OMPS-LP nor CALIOP have reported aerosol layers this high during that time. If it were a smoke layer at this altitude, one should expect a significant self-lofting of highly-concentrated plumes prior to this lidar measurement, which would be readily detected by satellite sensors.
l.435-440. While the wildfire smoke could, to some extent, contribute to the SA load perturbation after Summer 2019, I believe that the prolonged decay is largely due to the self-lofting of Raikoke sulfur-coated ashes as argued upon in this study https://www.nature.com/articles/s41598-022-27021-0 The self-lofting of aerosols is expected to prolong the aerosol removal from the stratosphere through gravitational settling.
l.439-440. I am unconvinced that the layers above 30 km could be attributed to Ulawun sulfates, please see my further remark on that matter.
l.498-509. The detection of hydrated layers from Hunga using RS and lidar in the northern midlatitudes is certainly an important result, however this should be supported by the respective graphical material.
l.548-552. In terms of the amount of injected material and injection altitude, the Ulawun eruption is nowhere near that of the 1991 Pinatubo eruption. Thus, appealing to modeling results by Stenchikov et al. for a major eruption appears to me unjustified.
l.557-558. Indeed, the absence of aerosols beyond 32 km after Pinatubo puts in doubt the attribution of layers above 30 km to the eruption of Ulawun. During the BDC-driven transport to midlatitude, the Ulawun sulfates would be exposed to warm temperatures and evaporate. This explains the absence of volcanic aerosols transported from the tropics at such altitudes. A much more plausible source of the high-altitude aerosols observed by the GP lidar, in my opinion, is the Australian ‘’Black Summer” PyroCb outbreak that generated a smoke-charged vortex rising up to 35 km whilst travelling towards the tropics. The fine smoke particles sediment slower than sulfuric acid droplets, which further corroborates this hypothesis. Another potential source could be the meteoritic dust. While an accurate attribution of the observed feature would require a careful analysis of various satellite data and transport modeling, I suggest elaborating this discussion a bit to consider various potential sources.
l.582. One should also mention particle sedimentation (e.g. Kremser et al., 2016), which does not fall under strat-trop transport category.
l.583. As far as the dilution and advection of clean air masses are concerned, it might be worth referring here to Vernier et al., ACP, 2011 and Khaykin et al., ACP, 2017 pointing out the poleward transport of convectively-cleansed air from the tropical tropopause region.
Citation: https://doi.org/10.5194/egusphere-2023-1781-RC2 -
RC3: 'Comment on egusphere-2023-1781', Anonymous Referee #3, 06 Nov 2023
General comments:
This paper documents one of the longest lidar records of stratospheric aerosols in existence. Changes in the instrumentation and analysis are followed through the record, and their implications for the data are assessed. Numerous volcanic eruptions and wild fires impacting this mid-latitude site in Germany are identified from sources in both the Northern and Southern hemispheres. This is a useful compilation for those wondering if a specific event impacted this region of the earth at a certain time. The absolute differences between events can also be reliably compared.
The paper is well written and only minor changes are suggested.
Specific comments:
Abstract: no comments
Line 45: Do you mean lifetime or 1/e folding time? I usually see about 1 year for these?
Line 129: “expensive additional laser photons”, do you mean you can use a smaller laser?
Line 153: The field campaign didn’t involve lidar right? It isn’t portable, but was controlled from the United States?
Line 165: “Afterwards, an extended-Klett (Klett, 1985) program, originally developed and very successfully quality assured for aerosol retrievals within EARLINET, is used”
Line 193: “The counting noise level in the raw data descends with altitude” Do you mean decreases with altitude?
Line 283: “(2018 “ missing “)”
Line 330: “…Northern Canada tree…”?
Line 430: “The temporary minimum of the integrated backscatter coefficient in September, 2019 is caused …”?
Line 494: “Not always stars exist …”?
Line 505: What do you mean by depolarized particles?
Figure 4: caption, “…Munich tropopause altitudes from the Munich radiosonde …”
Figures 16, 18, 19: Can you show the color scale? If all three figures use the same scale you could show the scale for just figure 16 and refer to that in 18 and 19.
Citation: https://doi.org/10.5194/egusphere-2023-1781-RC3 -
AC1: 'The reply to the four reviews received is contained in the Supplement.', Thomas Trickl, 30 Nov 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1781/egusphere-2023-1781-AC1-supplement.pdf
Interactive discussion
Status: closed
-
CC1: 'Comment on egusphere-2023-1781', Albert Ansmann, 18 Oct 2023
Dear Thomas and colleagues!
I read the manuscript with great interest. It is amazing to see this almost 50 year long time series of stratospheric aerosol observations, from 1976 to 2023.
The title of the manuscript points to the recent years (2017-2023) with a strong contribution of wildfire smoke to the aerosol in the stratosphere.
Because we from TROPOS worked a lot on this topic (and published several papers on wildfire smoke) I was forced to write a short comment.
Line 36: Yes, Mike Fromm pushed the smoke research forward (six references), but one could add even papers of Ohneiser et al. (ACP, 2022) on long term observations of Australian smoke (2020-2021) and Baars et al. (ACP) on Europe-wide Canadian smoke observations in 2017-2018.
line 42: The decay time should be well defined in the paper. The e-folding decay time was 13-15 months in the case of Pinatubo over Northern Germany (Ansmann, JAS, 1997) and 1.14 and 1.37 years over Japan and New Zealand (Nagai et al., SOLA, 2010, https://doi.org/10.2151/sola.2010-018).
line 60: Baars et al. (2019)
line 77: Are you sure that the Colorado fires were responsible for the smoke pollution in 2020? There were also long-lasting record breaking Californian fires during the 2020 summer half year, as described in Hu et al. (2022) and Mamouri et al. (ACPD, 2023).
line 261: …to more than 20 km (e.g., Baars et al. 2019, Torres et al., JGR, 2020 10.1029/2020JD032579).
line 285: Meanwhile it seems to be well established that pyroCb lofting followed by significant self lofting (as long as the smoke optical depth is high, during the first days after injection) enables the smoke to reach heights of more than 20 km or even more than 30 km (Torres et al, 2020, Khaykin et al., 2018, 2020, Ohneiser et al., 2023). There are many more papers on this topic in the recent literature.
line 297: For the same reason (impact of these lofting processes), the main message regarding the use and applicability of HYSPLIT trajectories should be that such a trajectory analysis can only describe the smoke transport when the lofting processes are (widely) over, when the smoke reached already heights in the lower stratosphere. The impact of pyroCbs and self lofting are not considered in these trajectory simulations.
line304: hot pyroCb is misleading….. after dissolution of the ‘cold’ pyroCb-related cirrus umbrella, smoke absorption and self lofting takes over.
line 332: Also the lidar at Hohenpeissenberg detected the aerosol in the free troposphere on 2 October 2017.
lines 343-345: In this context one should provide the reference to the paper in which the Leipzig observation are presented and discussed: Ansmann, Frontiers in Environ. Sci., 2021, doi: 10.3389/fenvs.2021.769852.
line 352: You assume that the smoke originated from strong Colorado fires? The articles of Hu et al., ACP, 2022, doi.org/10.5194/acp-22-5399-2022, Michailidis et al., ACP, 2023, doi.org/10.5194/acp-23-1919-2023, and Mamouri et al, ACPD, 2023 report smoke from record-breaking Californian fires. Maybe check again to be sure that Colorado fires were dominating.
line 403: To repeat, pyroCb contributes to the lofting of smoke, but also subsequently occurring self lofting of smoke.
line 414: You mean Boone et al. (2022)!
line 422: Do you think you observed volcanic ash or volcanic sulfate? Please discuss a bit.
line 550: Stenchikov et al. (2022) describes a similar scenario for Pinatubo aerosol as I tried to describe it for the smoke above. Pinatubo ash (plus SO2) was lofted (injected) up to about 17 km and then self lofting (as a result of absorption of solar radiation by ash particles) lofted the entire volcanic pollution higher up to 25-30km height (within a few days…). Then self lofting stopped because the high optical depth of ash disappeared by dilution and by sedimentation of ash particles. Then the sulfate layer formed in these lofted plumes with maximum heights around 30 km.
Figure 2: I do not understand! Please state clearly what you did! I speculate you applied the ozone correction to the lidar signals first and afterwards you applied the Klett method to the ozone-corrected signal profiles?
Figure 7: Californian or Colorado smoke?
Figure 10: Such a profile structure with aerosol within the upper troposphere as well as in the lower stratosphere on 22 August 2019 (red profile) was also found over Leipzig on 14 August 2019 (Ansmann et al., Frontieres, 2021) and assigned as smoke layer because of the high 532 nm lidar ratios (unusually high compared to volcanic sulfate lidar ratios published by Horst Jaeger). The fact that the aerosol layer was not clearly above the tropopause seems to be a hint that this is some kind of an undefined aerosol layer, partly containing smoke in the lower part and volcanic sulfate in the upper part.
All in all a nice…., or better an excellent work!
Citation: https://doi.org/10.5194/egusphere-2023-1781-CC1 -
RC1: 'Comment on egusphere-2023-1781', Juan Carlos Antuna-Marrero, 20 Oct 2023
The manuscript reports the characterization of the stratospheric aerosols layer enhancements over Central Europe produced by explosive volcanic eruptions and severe smoke from big fires. To that end, lidar observations between 2017 and 2023 at Garmisch-Partenkirchen, one of the longest stratospheric aerosols lidar records is used. It has been extensively used for research up to the present as the references show.
The manuscript’s scientific significance and scientific quality are excellent. The presentation is also excellent.
The description of the main features of the lidar instrumentation evolution and the most relevant aspects of the retrieved signal processing are included appropriately. Also, the discussion in the Annex of the contributions to the aerosol backscatter uncertainties is very important. It addresses relevant scientific questions for ACP Journal, in particular the characterization of the vertical and temporal evolution of the stratospheric aerosol optical properties originated from severe smoke from big fires and explosive volcanic eruption. All those facts warrantees the traceability of the results. The time frame are the last 6 years in which the frequency of those severe smoke from big fires has increased without a plausible explanation so far.
The scientific results and conclusions are presented in a clear, concise, and well structures way with an appropriate number of figures and tables. It gives appropriate credit to similar research and clearly indicates its own contribution. The manuscript title is appropriated, reflecting its content. Similarly, the abstract provides a concise and complete summary.
The references area appropriated in quality and number as well as the supplementary material.
I have some comments and suggestions listed below.
Comments:
In the section “Spectacular pyro-cumulonimbus in British Columbia on 30 June 2021”, the Figure 8 shows the aerosol backscatter uncertainty profile allowing to appreciate its reasonable magnitude respect to the aerosol backscatter. However, that is not possible for the two peaks going beyond the border of the figure. I suggest the authors include a brief description of the relative magnitudes of the uncertainties at the peaks in comparison with the relative magnitudes of the uncertainties from the rest of the profile.
Line 26: In the sentence: Ground-based lidar with its good vertical resolution became an important tool “almost” right from the beginning…. I suggest eliminating the word “almost” and add 2 more references: Fiocco, G., and G. Grams, 1964 and Elterman et al., 1973.
The first series of stratospheric aerosol profiles from lidar (Fiocco, G., and G. Grams, 1964, https://doi.org/10.1175/1520-0469(1964)021<0323:OOTALA>2.0.CO;2 ) and from searchlight (Elterman, et al., 1964, https://doi.org/10.1175/1520-0469(1964)021<0457:AAOWSP>2.0.CO;2) were extensively used for research on stratospheric aerosol from the middle of the sixties (after the Mt Agung eruption) until around the end of the seventies. They contributed to characterize the volcanic stratospheric aerosols vertical profiles evolution and the further advance of the scientific knowledge in the sixties and early seventies of the XX century. That is evidenced by the multiple articles referencing those results, including the references to Fiocco and Elterman provided in the two papers already cited in that sentence: McCormick et al., 1978; Simonich and Clemesha, 1997.
Elterman himself carried out research using Fiocco´s and his own datasets, (ex. Elterman et al., 1973 https://doi.org/10.1364/AO.12.000330; Elterman,1976 https://opg.optica.org/ao/abstract.cfm?URI=ao-15-5-1113).
Line 342: For clarity I suggest to change the sentence: ” The high lidar ratio suggested that observed at stratospheric aerosol at high latitudes were caused by import of fire smoke from Siberia.…”
By “The observed stratospheric aerosol high lidar ratio suggest its origin was the fire smoke from Siberia”
Line 487: Is this sentence referring to figure 18.? There is not an October 19 profile in the figure, unless the one from that month was labeled as October 10, before the date cited in the sentence.
Line 1020: The link http://www.trickl.de/Rayleigh.pdf does not work.
Figure 3: 4th line in the caption. The acronym “PSC” is not defined in the text, been used commonly for Polar Stratospheric Clouds. The Quebec (1991) and Chilshom (2001) fires mentioned do not appear to be related to PSC events. Please correct or clarify it.
Figures 7: Add the wavelength the aerosol backscatter coefficient was measured.
Figure 12: Briefly describe in the text the criteria to determine the upper and secondary boundaries of the top aerosol layer or provide a reference where it is described. Clarify the term main layer. Include in the caption the wavelength of the SCR. I suggest using the right axes scale for labeling the SCR magnitudes.
Citation: https://doi.org/10.5194/egusphere-2023-1781-RC1 -
RC2: 'Comment on egusphere-2023-1781', Sergey Khaykin, 30 Oct 2023
Review of Trickl et al., “Measurement report: Violent biomass burning and volcanic eruptions: a new period of elevated stratospheric aerosol over Central Europe (2017 to 2023) in a long series of observations”.
The manuscript by Dr. Thomas Trickl and coauthors presents the updated time series of stratospheric integrated backscatter from the 50-yr long lidar profiling record at Garmisch-Partenkirchen and focuses on the lidar observations of stratospheric aerosol layers produced by intense wildfires and volcanic eruptions since 2017.
The authors should be congratulated for an impressive effort to produce such a long-term and high-quality observation record of stratospheric aerosol loading as well as for their rigorous approach to data quality and error budget assessement.
The manuscript is well structured, the experimental setup and the quality aspects are described in a comprehensive way, whereas an appropriate credit is given to the related literature. Overall, the study represents a valuable contribution to the stratospheric aerosol problematics from the observational perspective.
In my opinion, the study could potentially be a good match for the “Research article” category had it included a more profound analysis of the locally observed features (beyond attribution to a specific event using simple trajectory modeling), or had it provided new information on the aerosol optical properties from various sources or otherwise re-evaluated different transport pathways and their timescales. While there are several novel aspects invoked (e.g. BDC-driven transport of aerosols, prolonged stratospheric aerosol decay etc.), the related interpretation largely rests upon general considerations without appropriate support from other data sources, in particular the global observations.
The high-quality local observations presented in the paper will surely motivate further research on the topic using global observations and modeling experiments. Therefore, in no way the “Measurement report” category could reduce the scientific impact of this paper. I recommend it for publication in ACP after a few minor revisions as suggested below.
Specific remarks
l.336-337. It is indeed very interesting (and also puzzling) why the backscatter enhancements are restricted to the lower part of the ozone enhancements. Could it be linked to aerosol sedimentation within the intruded airmass? I would be extremely curious to see the time curtains of backscatter (or just the range corrected signal) together with ozone curtain if this is not too much work.
l.379. Is the upper boundary of enhanced aerosol layer at 19.5 km attributed to wildfire smoke? To my knowledge, neither OMPS-LP nor CALIOP have reported aerosol layers this high during that time. If it were a smoke layer at this altitude, one should expect a significant self-lofting of highly-concentrated plumes prior to this lidar measurement, which would be readily detected by satellite sensors.
l.435-440. While the wildfire smoke could, to some extent, contribute to the SA load perturbation after Summer 2019, I believe that the prolonged decay is largely due to the self-lofting of Raikoke sulfur-coated ashes as argued upon in this study https://www.nature.com/articles/s41598-022-27021-0 The self-lofting of aerosols is expected to prolong the aerosol removal from the stratosphere through gravitational settling.
l.439-440. I am unconvinced that the layers above 30 km could be attributed to Ulawun sulfates, please see my further remark on that matter.
l.498-509. The detection of hydrated layers from Hunga using RS and lidar in the northern midlatitudes is certainly an important result, however this should be supported by the respective graphical material.
l.548-552. In terms of the amount of injected material and injection altitude, the Ulawun eruption is nowhere near that of the 1991 Pinatubo eruption. Thus, appealing to modeling results by Stenchikov et al. for a major eruption appears to me unjustified.
l.557-558. Indeed, the absence of aerosols beyond 32 km after Pinatubo puts in doubt the attribution of layers above 30 km to the eruption of Ulawun. During the BDC-driven transport to midlatitude, the Ulawun sulfates would be exposed to warm temperatures and evaporate. This explains the absence of volcanic aerosols transported from the tropics at such altitudes. A much more plausible source of the high-altitude aerosols observed by the GP lidar, in my opinion, is the Australian ‘’Black Summer” PyroCb outbreak that generated a smoke-charged vortex rising up to 35 km whilst travelling towards the tropics. The fine smoke particles sediment slower than sulfuric acid droplets, which further corroborates this hypothesis. Another potential source could be the meteoritic dust. While an accurate attribution of the observed feature would require a careful analysis of various satellite data and transport modeling, I suggest elaborating this discussion a bit to consider various potential sources.
l.582. One should also mention particle sedimentation (e.g. Kremser et al., 2016), which does not fall under strat-trop transport category.
l.583. As far as the dilution and advection of clean air masses are concerned, it might be worth referring here to Vernier et al., ACP, 2011 and Khaykin et al., ACP, 2017 pointing out the poleward transport of convectively-cleansed air from the tropical tropopause region.
Citation: https://doi.org/10.5194/egusphere-2023-1781-RC2 -
RC3: 'Comment on egusphere-2023-1781', Anonymous Referee #3, 06 Nov 2023
General comments:
This paper documents one of the longest lidar records of stratospheric aerosols in existence. Changes in the instrumentation and analysis are followed through the record, and their implications for the data are assessed. Numerous volcanic eruptions and wild fires impacting this mid-latitude site in Germany are identified from sources in both the Northern and Southern hemispheres. This is a useful compilation for those wondering if a specific event impacted this region of the earth at a certain time. The absolute differences between events can also be reliably compared.
The paper is well written and only minor changes are suggested.
Specific comments:
Abstract: no comments
Line 45: Do you mean lifetime or 1/e folding time? I usually see about 1 year for these?
Line 129: “expensive additional laser photons”, do you mean you can use a smaller laser?
Line 153: The field campaign didn’t involve lidar right? It isn’t portable, but was controlled from the United States?
Line 165: “Afterwards, an extended-Klett (Klett, 1985) program, originally developed and very successfully quality assured for aerosol retrievals within EARLINET, is used”
Line 193: “The counting noise level in the raw data descends with altitude” Do you mean decreases with altitude?
Line 283: “(2018 “ missing “)”
Line 330: “…Northern Canada tree…”?
Line 430: “The temporary minimum of the integrated backscatter coefficient in September, 2019 is caused …”?
Line 494: “Not always stars exist …”?
Line 505: What do you mean by depolarized particles?
Figure 4: caption, “…Munich tropopause altitudes from the Munich radiosonde …”
Figures 16, 18, 19: Can you show the color scale? If all three figures use the same scale you could show the scale for just figure 16 and refer to that in 18 and 19.
Citation: https://doi.org/10.5194/egusphere-2023-1781-RC3 -
AC1: 'The reply to the four reviews received is contained in the Supplement.', Thomas Trickl, 30 Nov 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1781/egusphere-2023-1781-AC1-supplement.pdf
Peer review completion
Journal article(s) based on this preprint
Data sets
Garmisch-Partenkirchen stratospheric aerosol series Horst Jäger, Helmuth Giehl, Matthias Perfahl, Thomas Trickl, and Hannes Vogelmann https://www-air.larc.nasa.gov/missions/ndacc/data.html#
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Thomas Trickl
Hannes Vogelmann
Michael Fromm
Horst Jäger
Matthias Perfahl
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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